The invention relates to a thyristor formed of a semiconductor body with a plurality of n-emitter zones provided with corresponding cathode parts. A p-base adjacent to the n-emitter zones is provided along with a p-emitter contacted by an anode. An n-base is provided between the p-emitter and the p-base. Controllable emitter shorts are provided at a boundary surface of the semiconductor comprising MIS field effect transistors of a depletion type, said emitter shorts being provided at edges of the n-emitter zones.
Such thyristors are known, for example, from German OS No. 29 45 366 A1 and German OS No. 31 18 354 A1, respectively corresponding to U.S. Ser. Nos. 199,633 filed Oct. 22, 1980 and 370,497 filed Apr. 24, 1982, both incorporated herein by reference. A common control voltage terminal is respectively provided via which a gate voltage is supplied to the MIS structures. In case such a thyristor has fault locations such as holes or weak points in the gate oxide, then the gate voltage applied when triggering collapses due to the short-circuit existing at the fault locations. As a consequence, the controllable emitter shorts constantly remain in effect and the thyristor can no longer be triggered. The density of fault locations is usually so high that a selection of faultless units would lead to a very low yield, particularly in the case of large-surface thyristors.